Volume 45 Number 4 Article 1

Great Basin Naturalist

Great Basin Naturalist

Volume 45 Number 4 Article 1

10-31-1985

Life history of the cui-ui,

Life history of the cui-ui, Chasmistes cujus Chasmistes cujus Cope, in Pyramid Lake, Cope, in Pyramid Lake,

Nevada: a review

Nevada: a review

William F. Sigler

W.F. Sigler and Associates Inc., Logan, Utah

Steven Vigg

University of Nevada, Reno

Mimi Bres

George Washington University, Washington, D.C.

Follow this and additional works at: https://scholarsarchive.byu.edu/gbn

Recommended Citation

Recommended Citation

Sigler, William F.; Vigg, Steven; and Bres, Mimi (1985) "Life history of the cui-ui, Chasmistes cujus Cope, in

Pyramid Lake, Nevada: a review," Great Basin Naturalist: Vol. 45 : No. 4 , Article 1.

Available at: https://scholarsarchive.byu.edu/gbn/vol45/iss4/1

This Article is brought to you for free and open access by the Western North American Naturalist Publications at

BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU

ScholarsArchive. For more information, please contact [email protected], [email protected].

The Great Basin Naturalist

Published

AT Provo,Utah,by

Bricham Young

University

ISSN

0017-3614

Volume

45 31October 1985 No.4

LIFE HISTORY OF THE CUI-UI, CHASMISTES CUJUS COPE,

IN PYRAMID LAKE, NEVADA: A REVIEW

WilliamF".Sigler',StevenVigg",and MiniiBres'

Abstract— Thecui-ui, ChasmistcsciijusCope,amemberofthe .sucker familyandendemictoPyramid Lake, Nevada,islisted asendangeredbytheU.S.FishandWildlife Service.Cui-uiwas onceamajor sourceofsustenancefor nativeAmericans,whohave inhabitedtheLahontanregionfor atleast11,000years.TheNorthernPaiutesdeveloped sophisticated fishingtechnologytoharvestthisresource.Theoriginal distribution of cui-uiwasthe ancientLake Lahontancomple.x,butasa resultof climaticchangesitwasrestrictedtothePyramid-Winnemucca-Truckeesystem by the turn of the20thcentury.Transbasinwaterdiversions(190.5topresent)haveresultedinfurther restrictions of habitat.ThespeciesisnowlimitedtoPyramid LakeandthelowerTruckeeRiver.Reproductionisfromhatcheriesas wellaslimited naturalreproduction.Femalesproducemorethan40,000

2-mm

eggsperyear.Thenormal develop- mentisdescribed fromthe unfertilizedegg through 912 hourspost-hatching,whenthefryare activelyfeedingand approachingadultbodyform.Theunusualfeature ofadult cui-uimorphologyisthe relatively largeventro-terminal

i

mouth, withthinand obscurelypapilloselips.Cui-uigrow^slowlyandmaylive18 years or possiblymuchlonger; femalesgenerallylivelongerandattainagreater sizethanmales.Thehighest adult mortalityprobably occursduring spawningruns.Atthistime theyarevulnerabletopredation,stress,andsometimes environmentaldegradation.The highestlarvalmortalityprobably occursfrom predationwhentheyareplantedormigrateintothelake.Thetrophic ecologyof the speciesispoorlyunderstood,but theyareknowntoingestalgaeand zooplankton.Spawningbehavioris

documented. Atpresent, naturalreproductionisprobablystillthe limiting factorforthe cui-ui population.Cui-ui ccMHposedlessthanonepercentof thetotal fish inPyramid Lakedining 1975-1977.During1982the largest cui-ui spawning run(13,000)inrecentyearsoccurred.Theacti\it\'of cui-uiinthe lake closeK'resemblesthatof theTahoe

^^uckerbeingmostactiveduringthespawning season eachspring. C'ui-uiinhabit theinshore-benthiczone andthe

^

^{pelagicwatersofPyramidLake(<46m).}

The

cui-ui, ChasmistescujiisCope,a

mem-

reachedits

maximum

sizeofabout 22,300

km'

ber ofthe sucker family (Catostomidae), is

some

13,000 years before present (BP) and present onlyin

Pyramid

Lake andtheaffluent inundatedalargeportion ofnorthwesternNe- lower Truckee River,

Nevada

(Fig. 1). Be- vada.

The

cui-uiwaspresentin

Winnemucca

cause ofitslimitedrange anddepleted

num-

Lakeuntilthelate1920s or early1930s(Fig. bers,itislisted asendangered(Federal Regis- 2).

ter.Vol.32/48, 11 March,1967). Cui-uiuntil Thereisgeneralagreementthatthe ecologi- recently was an important food source for cal devastation ofthecui-ui's lake andriver Northern Paiute, the native Americans

who

environment was causedinpartbythe

New-

have inhabited the regionfor at least 11,000 landsReclamation Irrigation Project (NRIP), y ^years.Prehistoricallythe habitat ofcui-uicon- which wasauthorizedbythe U.S.Congressin n sisted ofthe Lake Lahontan system, which 1903. In1905

Derby Dam

wasdedicated,and

'W.F.Sigler& AssociatesInc.,309 East 200 South. Logan, Utah 84321

"BiologicalSciencesCenter, Desert ResearchInstitute,University ofNevadaSvstein,Reno.Nevada DepartmentofBiologicalSciences,GeorgeWashington University,W'asliington.D.C.

571

572

^Great

Basin Naturalist

Fox

Valley

Needles

Cormorant

Rock

True

North

Hells

Kitchen

Anderson Bay

Dago Bay

Truckee

River

Popcorn

Fi«.^1. liatlivinrtricniapolT'Mann.l Lake,N.'Nada;cU'iUlio.ntou Icisatrlrvation 1154.9in.

October 1985 ^{SiCLER ETAL.: Cui-UlIN PVHAMII)}

^LAKE

⁵⁷³

WINNEMUCALAKE

; MudLakeSlough

ToLahonton Reservoir

Fig.2. TheTruckee River- PyramidLakeEcosystem.

574

transbasinwaterdiversionfrom theTruckee RivertotheCarson River system began. La- hontan

Dam

on the Carson River

was com-

pleted in 1915, creating Lahontan Reserv- ior

—

thewaterstorage

imponndment

forthe

NRIP. From

1915to1970as

much

ashalfor

more

ofthetotal flowof the lower

Truckee

River wasdivertedto the

NRIP.

Because of droughts

and

diversions,thelevelof

Pyramid

Lake declined

more

than24.4

m

from 1909to 1968,

Pvramid Lake

increased in total dis- solvedsolids(TDS) from about 3500to5500 mg/1,

and Winnemucca Lake

disappearedin 1938.

A

deltadevelopedatthe

mouth

ofthe Truckee River in the early 1930s that was virtuallyimpassabletospawningmigrationsof cui-ui. Naturalreproduction inthe

Truckee

River was verylimitedforabout50years (un-

tilthe

new Marble Blufldam

andthe fishway

became

functional for cui-ui in 1982).

How-

ever,duringyears of exceptionally highflow, naturalreproduction

may

have

been

possible. Upstream, Siphon

dam

(washedoutin1958), and about1mile

below

itthe original

Marble

Bluff"

dam

(washedoutin1950)

were

alsobar- rierstomigratingcui-ui.Neitherofthese ob- structions had functional fish ladders.

The

original

Numana Dam

alsobarredcui-uimi- gration.

Itisourobjectivetosynthesizeinformation collectedduringthe

Pyramid

LakeEcological Study,conducted

by W.

F. Sigler

_&

Associ- ates Inc. during 1975-1978, with available datafromagencyreports

and

research publi- cationstopresentan overview.Itis

hoped

this paperwillcontributetothe

knowledge

ofthe cui-ui,

and

thatitsdeficiencieswillpointout areas

where

additionalresearchisneeded.

Historical

Over\

iew

Cope

(1883)firstdiagnosed

and

revised the genus Chasmistcsand

named

a

new

species C. ciijusfrom

Pyramid

Lake. In 1918,

Snyder

publishedthefirst lifehistoryinformationon C. cujus and other fishes of the Lahontan System; evenatthisearlydate

Snyder

consid- ered the fate ofthe cui-ui to be uncertain.

Sumner

(1940) collected environmentaland fisherydatafrom

Pyramid

Lake andtheTruc- keeRiver,compiledachronologyofthefish- ery, and stated that the major cause ofthe decline ofthe fisherywasthe transbasin dixer- sion ofTruckee Riverwater.

T. _J.Trelease, thefirstfisherybiologist for the

Nevada Department

ofFish and

Game

(NFG), didpreliminary

work

onthe diet

and

reproductionof cui-ui(La Rivers1962).Jonez (1955)and Johnson (1958) (both

NFG

biolo- gists)

worked

with cui-ui during the 1950s conductingevaluations ofcui-uibehavior

and

habitat.

La

Rivers

made many

observations overthe years

and

developedalifehistoryfor cui-ui,incorporatinginformationfromprevi- ousworkers.

Koch

(1972, 1973)supplied informationon

lifehistory,reproductivecharacteristics,

and

spawning behavior of cui-ui,

Koch and

Contreras(1973)advancedartificialhatching techniques,

and Koch

(1976)

summarized

available life history information.

The

U.S. Fish and Wildlife Service operated a cui-ui hatcheryin1974-75.

Pyramid

LakeFisheries (PLF)hasoperatedthe

David

L.

Koch

Cui-ui Hatcherysince 1977

and

has further refined hatchingandrearing technicjues.

In1971theU.S.

Department

ofthe Interior (DI) reported theclassification status ofthe cui-ui. Federalrestorationofthe speciesbe- gan in 1973 by the U.S. Fish and Wildlife Service

(FWS)

cui-ui recovery team. This

team

completedaDraftCui-uiRecovervPlan in 1977(Pyleetal.1977).

The

1982revision of the original Cui-ui Recovery Plan was ap- proved

bv

the

FWS and

reviewed

bv DI

(U.S. FishandWildlifeService1983).

In 1975the U.S.

Bureau

ofIndian Affliirs (BIA)funded studies on thefisheries ofthe Truckee River

and Pyramid

Lake.

The

results of the

Pyramid Lake

EcologyStudies,includ- ing dataoncui-ui ecology, arepresentedin Sigler

and Kennedy

(1978).

The

resultsofthe Truckee River studies are in preliminary

FWS

reports.McConnell,Galat,and Hamil- ton-Galat (1978) and Galat and

McConnell

(1981) discuss

Pyramid

Lakefish production in relation to potential changes in total dis- solvedsolids(TDS).

Inthe early196()sthe

NFG

developedplans forafishwa\ that

would

enableupstreammi- gratingfishtob\passthe deltaand enterthe lowerTruckeeRiver.

The

plans

were

submit- ted to the Fleischmann Foundation, Reno, Ne\ada, butthefacilitywas notfunded be- causetheFoundation could begivennoassur- anceofawater right.

The NFG,

alongwith the

FWS and

the U.S.

Bureau

ofReclamation

(_)ctober1985 SiGLER ETAL.: Cl'I-UI IN

PYRAMID LaKE

₅₇₅ (BOR), then developedplansfora largerand

more

elaboratefacility.

The NFG

alsolobbied with state and national agencies for the

Washoe

Project Act,which

made

fundingpos- sible(T.

J.Trelease personal

communication

1984).

The Washoe

Project Act was

made

much more

salable

by

the earlier develop- ment, largely

by NFG,

ofhighly successful Lahontan cutthroattrout,

Sahno

clarki Jicn- sluiivi,fishery.

In1975

BOR completed

the

Marble

Bluff" Fishway.

The FWS

operates the

Marble

Blufffacility

and

monitors

spawning

migra- tionsof cui-ui

and Lahontan

cutthroattrout.

Data

collected

by FWS on

cui-ui

spawning

populationsinthe lake

and

fishwayarepre- sented

by

U.S. Fish

and

Wildlife Service,

Nevada Department

of Fish

and Game,

(California

Department

ofFish

and Game

(1976),

Ringo and

Sonnevil(1977),

and

Son- nevil (1977a, 1977b, 1978, 1981).

The

age structure of cui-uiin 1978

was determined

bv

Robertson (1979).

Scoppettone

et al. (1981, 1983,

and

G.

Scoppettone

personal

communication

198.3)studied the

spawning

behavior

and

habitatre(|uirementsof cui-ui inanatural sidechannelofthe lowerTruc- keeRiver.

Researchonthe habitatand ecologyoffish species in

Pyramid

Lake was conducted by Vigg (1978a). Vertical distribution patterns and relative

abundance

are reported (Vigg 1978b, 1980,1981).

Researchontheeffectsofincreasinglevels of

TDS

oncui-uiwasinitiatedbvEarl Pvle of

FWS

during 1975-1978. Chatto (1979) pre- sented preliminarydataon hatchingsuccess ofcui-ui eggsinvariousproportions of Pyra-

mid

Lake water.

Lockheed Ocean

Sciences Laboratories

(LOSL)

(1982) studied the ef- fectsofvariouslevelsof

TDS

ontheembryos, larvae,andjuvenilesofcui-ui.

T._J.Treleasefirstreared larvaein1947,and

Kay

JohnsonandIvan

Young

(all

NFG

person- nel)raised

them

toadultsize

_—

about31cm.

Koch

etal. (1979)estimated

91.6%

hatching success in controls during nitrogen-species bioassays.

However,

they

were

unabletoob- tain definitive resultson toxicitybecause of high mortalityinalltreatmentsandcontrols.

Koch

(1981)conducted preliminary tempera- ture tolerance studies of cui-ui

embryos and

larvae.

Various morphological studies have

been

conducted on catostomid fishes, including cui-ui. Nelson(1948, 1949, 1961) studied the comparative

morphology

of the

Weberian

ap- paratus, the opercularseries, and the

swim

bladder, respectively. Miller and Evans (1965) studied the external

morphology

ofthe catostomid brain and lips. Snyder (1981a, 1981b, 1983) studied larval

development

of cui-ui, mountain sucker [Catostomus })hityrliynclius), and

Tahoe

sucker {Catostomustahocnsis)and preparedakeyfor their identification. Millerand Smith(1967, 1981) discuss the paleohistory, systematics, distribution,evolution,andstatusofeachspe- ciesoi'Chasmistes

.

Donald

R. Tuohy,

Nevada

State

Museum,

CarsonGity,hasconductedextensive archae- ologicalstudieswithin the

Pyramid

Lakere- gion; however, the data are largely

unpub-

lished.Archaeokjgicalfinds at

Pyramid

Lake are reportedbv Ting (1967)and

Tuohy and

Clark (1979). Hattori (1982) studied the ar- chaeologyofthe

Winnemucca

Lakearea

and

relates theimportance of aquatic resources, includingcui-ui, to

human

prehistoric habita- tion.

The

importanceofthefishery,especially cui-ui, tothe nativeAmericansisdiscussed

by

Bath(1978).

The

ethnographicrecord of Pyra-

mid

Lake Northern Paiute fishing is pre- sented bv Fowler and Bath (1981). Follett (1963, 1974, 1977, 1980, 1982) has studied cui-uiremainsinaboriginal deposits. Stewart (1941) discusses the cultureelementdistribu- tionsoftheNorthernPaiute.

Procedures

Cui-ui

were

captured with variable

mesh

bottom-setgill nets in

Pyramid

Lake

and

at the

Marble

Bluff^facilityontheTruckeeRiver. Vigg(1981) presents^adescription offishsam- pling design and methodology. For age

and

growthdata, fish

were weighed

tothe nearest gram,

measured

(nearest

mm),

and sexedin- ternally, exceptatspawningtime.Scales,op- ercula, otoliths,

and

fin rays

were

taken to

compare

accuracy of aging using different

bony

parts.

The

length-weightrelationshipis

expressed

by

the formula

_W =

aL*' (Sigler 1951),

where W ⁼

^weight(g),

L =

fork length (cm), anda

and

bare constants.

The

value of the constants (aandb) are calculated

by

the

576

method

ofleastsquares using log transforma- tionsofweightandlength(log

_W ⁼

loga

+

log blength). Validity of the aging

method

was determined by criteria suggested

by Van

Oosten(1923, 1929, 1944)andHile(1941).

To

avoid possible bias, scales and other

bony

parts

were

firstread without

knowledge

ofthe sizeofthefish.

They were

readat leastthree times.

The

length of

body-bony

partrelation- shipwascalculatedaccordingtoTesch(1971).

The

conditionfactor

K

^{=^}

Wxl07L^

wascalcu- latedaccordingtoCarlander(1969),

where W

=

weight(g)and

L ⁼

forklength(mm).

Age

and

growth calculations

were

accomplished usinga

computer program

(Nelson 1976).

Cui-ui eggsand

embryos

usedinthisstudy

were

obtainedfrom the

David

L.

Koch

Fish Hatchery.

They were

collectedatregularin- tervals postfertilizationand preservedinboth Bouin's solutionandPuckett'sfixative. Serial sections of the entire

embryo were

cutat

8-

10 micrometers

and

stained with hematoxylin

and

eosin and Mallory's Triple Stain.

Em-

bryos to be sectioned

were

chosen from

among

the bestpreservedof12-15specimens from each sample. In addition to sectioned material,whole

mounts were

alsoused, rang- inginagefrom9 to912 hourspost-hatching (Bres1978).

There were

19water samplingstationslo- catedalong 4 transectsdesignedtorepresent the horizontal areas ofthe lakeandto facilitate measuringthe influenceoftheriver

upon

the system. Stations

were sampled

ona

monthly

basisfrom

November

1975throughOctober 1977. Conductivity, oxygen,

pH,

tempera- ture,andturbidityinrelationtotime,depth, andlocation

were measured

inthefieldwith an InterOcean probe

(Model

513D).

Mea-

surements

were

taken at

2-m

intervals from the surfaceto22

m

andat

5-m

intervalsfrom 25

m

to thebottom. Conductivity measiue- ments

were

standardizedto25C.

Water

sam- ples

were

collectedforanalysisofmajor

chem-

icals and trace elements the third

week

of every

month

from January through

Decem-

ber1976 and againin April and

September

1977. Samplestobetestedfornutrients

were

collectedat leastoncea

month

from January 1976through

December

1977.

Water

sami)l('s

were

collectedatthe surface (Im), middeplh, and bottomlevels atthemidpointofeachol three transects (Lider 1978). Analyses

were

done

bytheDesert ResearchInstitute

Water

ChemistrvLaboratorv.

R\NGE AND

Distribution

Four

recent species of CJiasmistes are

known:

C. ciijitsCope, C. liurusJordan, C. hrevirosthsCope,

and

C. miiriei Miller

and

Smith;thelatterspecies,

known

fromasingle collection, is

now

extinct.

Two

additional ex- tinct species, C. bcitrachops

Cope and

C. spatulifer Millerand Smith, are

known

only fromthefossilrecord.Millerand Smith(1981) discussthe distribution andevolution ofthe variousformsoi'CJwsmistcs (Table1).

CJiasmistesisa lacustrinesucker;allliving speciesand mostextinctformsareassociated with lake systems.

However,

the oldest

known

form, CJiasmistessp. fromthefluvial bedsof the

Miocene Deer

ButteFormationin Oregon, is an exception (Miller and Smith 198i).

The Pyramid

Lakecui-uipopulation isthe last_remainingpurespecies ofthegenus; the other specieshaveconsiderable hybridization

and

introgression with Catostomus spp. (Miller and Smith 1981). Cui-ui inhabited

Lake

Lahontan during the late Pleistocene period(Fig. 3). At its

maximum

extent, ap- proximately 12,000yearsBP,Lake Lahontan covered about 22,300

km" and

received drainage from about 117,000

km"

(Russell 1885). Fossilcui-uihave

been

discovered in theCarsonDesert,which was once contained in thelargestbasin of

Lake

Lahontan; addi- tional CJiasmistessp. fossilshave

been

found in the

Honey

Lake basin to the northwest (Millerand Smith 1981). As

Lake

Lahontan desiccated during the last 10,000 years, its

contiguousbasin

became

nine

remnant

lakes. Cui-ui persistedforvariablelengthsoftimein these

remnant

watersuntildesiccationcaused extinctionofmostpopulations.Cui-uiwasnot present in

Walker

Lake during historical times.This ideaisconfirmed

by

the

work

of Spencer(1977)and

Benson

(1978a),whichin- dicated

Walker

Lake was dry

sometime

dur- ingtheperiod9050to6400yearsBP.

During historic times cui-ui li\ed in both P\lamidand

Winnenuicca

lakesand

spawned

in theTruckce Ri\erasfarupstreamasjust below

Reno

(Snyder 1918).

When Derby

Dam

was completedin1905, spawningcui-ui

October 1985 SiCLER ETAL.:CUI-UI IN

PYRAMID LAKE

₅₇₇ Table1. Thegeographicdistributionof recentandFossilspecies ofC7(rt.s»ii.sfr.v(Millerand Smith1981).

RecentSPECIES Commonname

C'lii-ui

June sucker

Shortnose sucker Snake River

sucker

Scientificname C.ciijusCope

C./lor^.vJordan^ C.I.

C.I.mictiis C. brevirostris

Cope C.miiriei

Millerand Smith

Drainagebasin Lahontan

Bonneville

Klamath River

Snake River

Presentrange Pyramid Lake,

Nevada Utah Lake,

Utah

UpperKlamath Lake,Oregon Extinct"

Fossil SPECIES Scientificname Chasmistessp. C. spatulifer

Miller

&

Smith Chasmistessp. Chasmistessp. Chasmistessp.

Chasmistessp. Chasmistessp. C.batrachops

Cope Chasmistes cf C.batrachops C.batrachops

Chasmistes cf C. liorus C.cujus

C.brevirostris

Geologicepoch Miocene Plioceneand

Pleistocene-Recent Pliocene

Pliocene Pliocene

Pliocene Pliocene Pleistocene^-

Recent Pleistocene^-

Recent Pleistocene^-

Recent Pleistocene^- Recent Pleistocene-

Recent Pleistocene-

Recent

Geologic fonnation DeerButte,

OR

GlennsFerry,ID

toAdrian,

_OR

GlennsFerry,ID Secret Valley,

CA

HoneyLake

sediments Calcareous sands Teevimom,

WY

FortRockBasin,

_OR

WhiteHills,

CA

Duck\'alley,

NV

BlackRockCanvon,

UT

Pleistocene gravels, Fallon,

NV

Indianmiddens, KlamathLake,

OR

Paleohabitat Fluvial Lakebeds

Lake beds Lake beds Lake

Lahontan MonoLake

Fossillake

ChinaLake

Pleistocene Lake LakeBonneville

LakeLahontan

Klamath Lake

A.Catostomus fecundus Chasmistesliorus >Catostomiisaniens B. Basedon asingle collectionfrom theSnake River below Jackson LakeDam

were

restrictedtotheriver

below

thatpoint. As waterwas diverted to the

NRIP

via the Truckee Canal, the water level in

Win-

nemucca

and

Pyramid

lakes dropped. VVin-

nemucca

Lakedriedin 1938.

Pyramid

Lake andtheaffluentlowerriveristhe onlyremain- ing habitatfor cui-ui.

Embryology

Koch

(1972, 1976) did limited

work

onthe larval

development

ofcui-ui, finding

many

similarities tothe

development

of thewhite sucker, Catostomus commersoni, as de- scribedby Stewart (1926).

Long

and Ballard (1976)

document

the stages of

embryonic

de- velopmentofthewhite sucker

and

citediag- nostic structural characteristicsforeachstage.

They

alsoreviewprevious

work

on embryol- ogyofotherfisheswithin theorderCyprini- formes.Snyder(1983)foundthatsequencesof developmental events are nearly equal for cui-ui,

Tahoe

sucker, and mountain sucker andtypical at least forthetribeCatostomini.

However,

thelattertwospecies,atanygiven size,areslightly

more

developedthancui-ui.

The

followingis adetaileddiscussion of the embryological

development

ofthecui-ui ina 13

C

environment(Bres1978).

Egg-Embryos

The

unfertilizedeggof thecui-uiisabout2

mm

in diameter and ^is surrounded

by

a noncellular chorion. Ithasone micropyleat theanimal pole. Afterfertilization, duringa process

known

aswater hardening, theeggs

578

Lake Lahontan

>

10,000 yearsB. P.

Remnant

Lakes

>

6400years B.P.

California

Utah

Arizona B.

Pyramid Lake

Winnemucca

Lake

Lower

TruckeeRiver

WINNEMUCCALAKE

PYRAMID LAKE

Sutcllffe

Before 1938

Pyramid Laketo MarbleBluff

Dam

D.

MudLake Slough

Nixon PYRAMID LAKE

DerbyDam

RENO/SPARKS

1975- Present

Fishway

MarbleBluffDam

Fi^.3. Dc'CR-aseintheniiiiieol'llu'cvii-uifromLakeI.alioiitontimestothepr

October 1985 SiCLER ETAL.;CUI-UIIN

PYKAMID LaKE

₅₇₉

imbibe water andswellto3

mm. Koch

(1976) recorded an

83%

increaseinegg

volnme

dur- ingwater hardening, whichtook39minutes. Trelease (personal communication 1984) recorded

75%

increasediningwater harden- ing and a time of 60 to 75 minutes.

The

blastodiscappearsat6 hourspostfertilization, 0.5

mm

indiameter,andiselevatedabovethe surfaceoftheeggat theanimal pole.

By

18 hours postfertilization, 8 blastomeres are present, withan exponential increasein

num-

berthereafter.After19 hours, "giant" nuclei areseenassociatedwiththe syncytialcellsof theyolksac.

The

marginalperiblastisatthe peripheryofthe blastoderm.

At 48 hourspostfertilization, the first dis- tinction

between

thethree

germ

layersisap- parent.

The

neural plate has formed, along withathickened precursortotheneural tube.

The

notochord

and

somites are present.

At 96 to 120 hours, the neural tube

and

notochord are well developed.

Myotomes

havedifferentiatedfromsomites,andthe dor- sal fin fold has

begun

to develop.

The

pronephricducts are

formed

anteriorallybut areundifferentiatedposteriorally.

The

gut has no

lumen

andisincompleteposteriorally,

and

the cloacahas not yetformed.

Anterior neural crest migration occurs at 144to168hours.

The

diencephalonexhibits cruciform shape.

The

optic vesicleshavede- veloping lenses, and the opticoel joins the diocoel. Auditory vesicles are also present. Myoblasts the length ofone somite can be seen.

The

coelomiccavityis developingbe-

tween

thesomaticandsplanchnic

mesoderm.

At 192 hourscranialganglia V, VII, and

X

arevisible. Presumptive medullaisdevelop- ing,andthelateralventricles are present.

The

pronephric ducthasincreasedinlength,and tubule

development

isbeginning.

The

liver diverticulumand developinggut arevisible. Vitelline circulation is well developed, and the dorsal aorta and postcardinal veins are visible. Precursors of the

pigmented

retina(a singlelayer ofcells)andtheneural retina are forminginthe eye.At13

C

hatchingoccursat 216hours.

Larvae

At hatchingcui-uiarewhiteandthreadlike inappearance,6to7

mm

inlength,without

Tabi.k2. Time.sequence ofeui-iiidevelopmentat13

A(;k

yolk

blastomere

Fig.4a. ⁱhourspostfertilization

oticvesicle

telencephalon

Fig. 4b. 9hourspost-hatching

Fig.4c. 4.5days post-hatching

October 1985 SiCLEK ETAL.:CUI-UIIN

PVKAMID LaKE

581

r-^'Ti.\'.'''j^ ^yi^.'':.

Fig. 4d. 21days post-hatching

Pig. 4e. 38 days post-hatching

Fig.4. Embryonicstagesofdevelopmentof the cui-ui

arevisiblealong the spinal cord.At384 hours theepiphysiscontinuestodevelop.

The

pitu- itaryand hypothalamusarevisible,although no differentiation has occurred in the pitu- itary.

Motor

neurons are welldeveloped in themesencephalon. At 504 hoursthedevel- opingchondrocraniumisvisible.

Eye

.

_— The

opticcup andretinacontinueto developafterhatchingoccurs.

The

opticchi-

asma

isfirstobservedat26to31hours(post- hatch),withthe opticnerveconnectedtothe retina.

The

horseshoe-shapedretina,derived from the optic cup, is apparentat 51 to 56 hours. At this time theoculomotor nerve is visible, extendingfrom the brainto theeye region.

By

72hoursthe lensispresentandthe

pigmented

retina is represented by a thin layer; however,

no

differentiation has oc- curred in thesensory portion of the retina. Presumptive corneahas

formed

by 84hours, anddifferentiation inlayersofsensoryretina has occurred.

The

opticnerveisattachedto theretina. Extrinsic ocularmusclesare well developed.

By

120hours,heavy pigmentation

has

been

laid

down

ontheretina. After384 hoursthe

pigmented

iris, cornea, lens, and

many

sensorylayersofthe retina arevisible.

The

eyesare functionaland capableof

move-

ment.

Ear and

LateralLine.

—

Seventy-two hours post-hatching,theotic vesicle, therudiment oftheinnerear, beginstodevelop.

The

first

completedistinction

between

the dorsalsac- culusandthe central utriculus takes placein theoticvesicleat84 hourspost-hatching.At this time the first _indication of lateral line system

development

occurs.

By

168hoursthe oticvesicleiswelldeveloped.After384 hours oflarval development, the otic capsule has dividedinto3parts,thelatterpartbeing

com-

pletelyclosedoff. Otoliths arevisible inthe innerear, andthecranialnervesthatsupply the ear arevisible.

The

vestibulargangliahas developedoutside the oticcapsulefrom the stato-acousticnerve(VIII).

Olfactory Sense

and

Taste Buds.

— By

²⁰ hours the olfactoryplacodes are well devel-

oped

inthe anterior portion of the head.

The

582

neuralconnectionofthe nasalplacodetothe brain (olfactorynerve)is visible

by

26 to31 hours.

By

168 hoursthe olfactoryorgan has developed from the nasal placode.

By

384 hoursindentations areformingatthesiteof the future external nares.

The mouth

isopen, and developing tastebuds arevisible in the

mouth

andgills

by

384hours.

These

arevery abundant on the head, mouth, and gills of adultsand

compensate

forincompletedevel-

opment

ofthe internal nares.

Gills.

_— Four

pairsofgillarches arevisible at26to31hours.

The

aorticarches leave the center of the gill arch to fuse together and

open

into the conus arterious. At 51 to 56 hourssix pairsofgillarches are present and thegillcleftisdeveloping.

By

60 hours eachof thesixpairsofwell-developedgillarches has a central core,theaorticarch.

By

72 hoursthe aorticarch has increased substantiallyin size. At 84 hoursthefirst gillclefthasopened.

By

312 hours the 6 primitive gill arches have

been

reducedto5 functionalgillarches, the definitive adult condition.

Each

arch has at least3 filaments

composed

of loops ofcapil- laries. After384 hours ofdevelopment, gill filaments are evident, as are gill cartilages associatedwithmusclesfor

moving

thegills.

Heart.

_— The

S-shaped heart is visible 9 hourspost-hatching.After20 hourstheendo- cardial cushion, which is the precursor to valve development, is formingin theatrio- ventricularcanal. Separation

between

endo- cardium and

myocardium

is

pronounced by

56 hourspost-hatching.

The

heartandassoci- ated vessels are welldeveloped

by

72hours. Cardiacjelly is visible after 82 hours. After 120hoursall4

chambers

of the heart

and

the atrio-ventricular canal are visible. After312 hoursthe muscularwall ofthe heart is well developed andthe ventricle has

become

tra- beculated.

By

384 hoursallbloodvesselscon- taineosinophilicplasma.

Muscle^.

— Myotomes

and

myocommata

are welldeveloped by9 hours.

By

26to31hours connectivetissue ispresentinthe

myocom-

mata.At 72 hoursmyofibrilsappearasribbons aroundtheperipheryof themusclecells;this conformstothestandard configuration of the adultfish.

Skeleton.

_—

After20 hours thesitesofthe future chondrification of theribsarevisible as individual swellings along the dorso-lateralin-

tersegmental myosepta.

By

51 to 56 hours condensationisbeginningtoformtheinitial skeletalelements.

The

trabeculae of thechon- docraniumarevisible,although theyare not truecartilagebut simply condensationsofthe

mesenchyme.

After312 hoursalarge

number

ofcaudal rays are present.At384 hourscarti- lageispresentinthegillarches,opercula,

and

the roof ofthe

mouth

(precursorto palate).

Liver

and

Pancreas.

_— The

liver pri-

mordium

^iswelldeveloped

by

20hours.At26 to 31hours the sinus venosus has

been

dis- placedtoacrescentshape atthe side of the liver.

The

liver

primordium

iswelldeveloped

by

84hours;apancreaticrudiment isvisible nexttotheintestinalswelling.

The

liverhasan adultpattern of organizationandisfunctional

by

384hours.

The

pancreasisforminglobules thatwill laterspread outforming the adult diffuse pancreas.

The

gall bladderisvisible; bileandpancreaticducts are separateandfuse togetherattheentrancetothegut.

Kidney.

_—

At9hoursthepronephricducts join with the intestine posteriorally to form the cloaca.

By

26 to 31 hours, ciliated nephrostomes, the opening of the kidney tubuletothecoelom, have developedinthe pronephros, and coelomic fluid is

pumped

intothe tubule. After72 hoursoflarvaldevel- opment, kidneytubules are welldevelopedin the pronephros. For the first time, the

mesonephros

and mesonephric tubules are visible. At 84 hoursthemesonephric ductis visible, opening into the

mesonephros and

contacting the cloaca.

By

312 hours the

mesonephros

has greatly enlarged, is very welldeveloped, andhasreachedafunctional state.At672 hoursthemesonephric duct

and

anus

empty

together into thecloacalaperture. Alimentary Canal.

— ^The

^{pronephricducts}

joinwiththe intestine posteriorlytoformthe cloaca9hourspost-hatching.

The

tiny, solid gutbegins toform theloop of the intestinal swellingatabout20hours.

The

larvalcui-ui, likethe adults,

do

nothave atrue stomach sinceitcontainsnoglands. At 26to31hours the secondarx reopeningofthe gut begins, small in theliver mass butenlarging inthe midgutregion posteriortotheliver.

Mesen-

teriessupportingthe gut arevisible.Absorp-

ti\ecellsareapparentinthe yolksac,

and

the

mouth

cleftispresent. Furtherrecanalization oftheIbregutisoccurringat51to56hours.At

October 1985 SiCLER ET^AL.:CUI-UIIN

PYRAMID LaKE

583

72hoursthere are

many

secondaryopenings inthe foregut. Also the

hnnen

ofthe gut has greatly increased fiom 1 to 2 to 10 to 15 micrometers in diameter. At 84 hours the loops of the gut arebeginningtoform; early differentiation oftheintestinal swelling

and

visceralcavityoccurs.

The

pharyngealcavity

is

open

at 120 hours. After 384 hours the

mouth

is open, and

many

mucous-secreting cells are visible in the oral cavity. Material presentin the pharyn.x suggests feeding, al-

though

some

parts of the pharynx are still

undifferentiated.

The

gutisbroadly

open

and hasdevelopinglongitudinal folds.

From

384 to504 hoursthe yolk sacisgreatlydiminishing insize.After672 hoursoflarvaldevelopment, the yolkisabsent

and

thegut isfunctional, with food present in the intestine.

By

840 hoursthe larvae are20to25

mm

long(Koch 1976).After912 hoursfryare activelyfeeding andthe digestivetractisfilledwithfood.

Integument

and

Pigmentation.

_— By

20 hourslateralfinfoldsarewelldeveloped,and

many mucous

secretingcellsarevisible inthe ectoderm. Connectivetissueispresentinthe dermisofthe skinat26to31 hours. After72 hourstheepitheliumisstillsimple,and

many

secretorycellsarepresent.

Melanophore

de- velopment is beginning internally. At 84 hoursgobletcellsareobservedinthe epithe- lium. Granularcells, filledwith eosinophilic granules, are present, characteristic ofthe adult condition. Bothsmallandlargeexternal melanophoresarevisibleby 120 hourspost- hatching.At384 hours mucous-secreting gob-

letcellsarepresentintheskin.

Swimming

^.

—

^{After 18hours}the larvae are 8 to9

mm

long, and

sudden

bursts ofenergy constitutetheirinitial

swimming

attempts;at 192to240 hoursthe larvae are 12to14

mm

in length and continually

swim

at the surface (Koch 1976).

Between

240to360 hours they

swim

to keep their position in the water

column

(Koch 1976). After 384 hours the pneumatic ductenters the gutfromthe devel- oping

swim

bladder, and at 504 hours the

swim

bladder is clearly visible.

The swim

bladder has increased in size during 672 hours.

Identification.

_—

Larvalandjuvenilecui-ui aresometimesdifficulttoidentifyin

Pyramid

Lake; they areeasily confused with another resident catostomid, the

Tahoe

sucker. This

may, inpart, account for the fact that rela- tivelyfewcui-ui lessthan 300

mm

inlength have

been

identified.

Ramsey

(letter toE. A. Pyle,16September, 1974)offersthe following pointsof contrast

between

thetwolarvae:

Ventral-Pi^incntation:Aconsistent characterfor dis- tinguishine;lar\ al_{stages of}Tahoesuckerfromlarvalcui-ui isthepresenceof a superficialrowofmelanophores onthe midventralskinposteriortothe pectoralbasis.Thisab- dominal pigmentationisgenerallyabsentincui-ui, al- thougharowofmelanophores sometimesispresentbut confinedtothe breast anterior to the pectoral bases.The rowofmidventralmelanophoresinlarvalTahoesuckersis stillpresentatage66 days(17to19

mm

totallength).

Intestinal Coiling:At age 66 daysthe intestine of the Tahoesuckerloopsfaranteriorincontrasttothe cui-ui, whereitiseither straightor has alefttwist.

Mouth:ThelipsoftheTahoesuckerarethickerandthe mouthisplacedfurther ventrallythaninthe cui-ui.

Other:Acharactersometimesusefulatagesearlier than66 daysisthepresenceincui-uiof adepigmented

"onetoone"ontop of thehead,justposteriortothe eyes. Thereisconsiderableoccludingofthispigmentationby age66days.

Snyder(1981a,1981b, 1983)studyinglarval

development

ofcui-ui incomparison to the other catostomids that

spawn

intheTruckee Riversystem, i.e.,

Tahoe

suckerand

moun-

tainsucker, developedataxonomic key that separates the larvaeandearlyjuveniles ofthe three species. Snyder concludes the larvae can be separated onthebasis ofmidventral pigmentation, peritonealpigmentation, gut- loop formation,and

mouth

characters.

The

followingdifferentialcharacteristicsare included to

complement

previous descrip- tionsoflarval

development

and

morphology

(Snyder1983).Atatotallength (TL) of 11to21

mm,

cui-ui are characterized by absence of midventralmelanophores ontheheador ab-

domen

anterior to the bases of pelvicfinor theirprecursorsandanterior tothe vent. If midventral melanophores exist, they are presentasashort lineonly inthe branchial and heart regions

between

and anterior to pectoralfinbases. Mesolarvae haveastraight gutuntilabout 19

mm

TL; metalarvaeto21

mm may

develop aprimary loop extending foi-wardless than two-thirds of the length of thestomachandnot crossingoverthestom- ach. Metalarvae have peritoneal pigmenta- tionlargely restricted tothe dorsalanddor- salateralvisceral cavity.

The

followingcharacteristicsapplytometa- larvae

>

21

mm

andjuveniles

<

50

mm. The

pigmentationof theperitoneumismostlylim-

Fig.5. Adult femalecui-ui.Photoby Thomas_J.Trelease.

ited tothe dorsalanddorsalateralvisceralcav- ity.

The

primaryloopofthe gutis relatively straightalong theleftside of thestomachuntil about 30

mm

TL, at

which

size secondary loops cross thestomachinanS-shape,persist- ingthrough50

mm

TL.

The mouth

istermi- nal

_—

usually slightlyoblique but sometimes very low and almosthorizontal,approachinga subterminalcondition.

Adult Morphology

Description

The

cui-ui isa large,

big-mouthed

sucker.

The

head ^is

wide and somewhat

roimd in cross-section.Itsinterorbitalspaceisgreater than half the length of the head.

The mouth

is

unsuckerlikewithaventro-terminalposition.

The

lipsare thin

and

obscurelypapillose.

The

lowerlipis

somewhat

pendantand divided

by

awide

median

notch.

The

cui-ui iscoarsely scaled,with countsof 13to 14above thelat- eral line,59to66ak)ng thelateral seriesand 22to26aroundthecaudalpeduncle.

The

total

body

lengthis9 times that ofthe dorsal fin base.

The

length of the anal fin, from the insertiontothetip,isaboutonesixththetotal

body

length. Fin raycountsare: dorsal, 10to 12; anal,7;andcaudal,8 orless.

The

caudal^is

weak

to moderatelyforked.

The

caudal pe- duncleisthick,withthe smallestdepth going 12times into standard

body

length (SL). In triangular section, the pharyngealteeth are delicate.

The

^lastpharyngealarch bearsa

row

of

more

than10combliketeethconfinedtoa single row.

The swim

bladderis2-celled; the peritoneumisnearly black.

Each

gillrakeris

branchedlikebroccoli(Fig.5).

Sexual

Dimorphism

Breeding males display a brilliant red to brassy coloronthesides; in generaltheyare black or

brown

above, fading intoflatwhite below.

Females

haveabluish graycastyear- round.

Female

cui-ui attain greater length

and

heavier weightthan males.

During

the spawning seasontheventoffemales

becomes

swollen

and

extended, whereas males de- velop nuptial tuberclesontheirfins. Appar- ent sexual

dimorphism

exists inthe meristics associatedwithfinsize(Table3).

The

length of thebaseof the dorsalandanalfins,the height of the dorsalandanalfins, andthe length of the pectoral, peKic, and caudal fins are all proportionally greater for males.

Snyder

(1918)refers todifFerences

between

thesexes: Tlu'femalesaremorestockythanthemales,and with theirhugeheads, largeroundedbodies,andrelati\el\

October 1985 SiGLER ETAL.: CUI-UIIN

PYRAMID LaKE

₅₈₅ Table3. MeristicsofChasmistescujtisfrom nearthe

mouth^{of the}Truckee River (Snyder1918).

faciallobe of the brainisassociatedwithtaste buds onthelips

and

skin,whereasthe vagal lobes receive fibers from taste buds in the

mouth and

pharynx.

The

brain

morphology

of cui-ui is unique in several ways: the optic lobes are small

and

separated, the postcere- bellar medulla is elongated,

and

the vagal lobes are well developed but located

more

posteriorlythanisusualincatostomids.

The

overall pattern suggests a well-developed

"mouth

tasting"apparatus(Millerand

Evans

1965). Suckersthathavelarge vagallobes are characteristic of lotic habitats, and

mouth

tastersprobablysortfood within theoralcav- ity.

Thus

thecui-ui is probablynot a sight- feederinsurfacewaters but

may

usetheoral cavityto sortoutfood(e.g.,algaeandinverte- brates).

Other

genera with well-developed vagallobesincludeXyrauchen,Ictiohus,

and

Carpiodes.

Age AND Growth

The

cui-uiisaslow-growing,long-livedfish, living 18 or

more

years (Robertson 1979). Scoppettone(reporttoDesertFishesCouncil 1983) statedit

may

live

much

longer(>40).

Growth

in lengthis rapidforthefirst4 to5 yearsand slowerthereafter. Annuli inolder fishare

formed between

June

and

August;in younger fish it

_may

occur the first

week

of June.

Back-calculated fork length(FL)atscale for- mationis46.0

mm

for

known

agefish(1to111),

from the

NFG Washoe

Rearing Station, Reno.

The

calculated

FL

was

skewed

substan- tially higher

when

advanced age groups (IV andVI)from

Pyramid

Lake

were

added. In aquarium-rearedfish,E. Pyle (personal

com-

munication 1977)found theystartedforming scales at49.0

mm

FL, and fish 50

mm

had from3 to 7 scales atthe base ofthe caudal peduncle.

Scalesarejudgednottobereliable foraging cui-ui older thanageVI. Other

bony

parts, otolith,opercula,and^finray,are

more

nearly reliable.

No

techniqueisreliable

when

there

isno,oralmost no,growth and nodiscernible annulus. Thisisa definitepossibility inolder cui-ui. There is reasonably good

agreement

between

fin rays and otoliths and excellent agreementl)etwcen otoliths and

operculum

through ageXIII (Table4).

There

was gener-

£ ⁵⁸⁰

T

E 560

1415 16 1718

Annulus

Fig.6. Absolutegrowthratesusingfourmethodsof ageassignment(scales, finrays,operculum,andotoliths) forcui-uicollected fromPyramidLake, Nevada, 1978 (Robertson1979).

allygood

agreement

for otolith,opercula,

and

scale inageIto IV. Data from opercula

were

chosen because^itisreliable

and

easytocollect and process. Since growth differences

were

notsignificant,sexes are

combined

(Table5).

The

absolute growth ^is in good

agreement

withcalculatedgrowth(Fig.6).

The body

fork length-opercula(X)relationship, sexes

com-

bined,is:

_FL -

229.2

+

7.0x(r

=

0.92).

The body

length-bonypart radius regres- sions arehighly correlated:finray(r^

=

0.93), opercula(r"

=

0.92), otohth(r"

=

0.80), and scales(r'

-

0.63)(Robertson1979).

The

dropinniunbersoffisholder thanage

XV may

beattributed largelytonaturalmor-

talityorno growth, but thelow

numbers

of fishin

some

ottheyounger age groupsare, in part,a resultofmoderateto

weak

yearclasses (Table 6). Sonnevil (1978) suggests reduced spawning populations and consecjuent

weak

yearclassescanbeattributedtoreducedriver flowsatthetimecui-uispawn.

There

appears to be good correlation be- tweenstrength of yearclassesandflowlevels of the river for5 ofthe 12 years and poor correlationfor3 of the 12 years (Table7).

October 1985 SiCLER ET^AL.:CUI-UIIN

PYRAMID LaKE

₅₈₇ Table4. Comparisonofassigned age by^variousagingmethods(or28c

1978 fromPyramidLake, Nevada.

sexescombined. CollectedApriltoJuly

Methodsof age assignment

588

Table6. Ageand yearclasscompositionof665cui-ui sampled in Pyramid Lake, Nevada, 1978 (Robertson 1979).

Ageclass

October 1985 SiCLER ET^AL.: CUI-UIIN

PYRAMID LaKE

₅₈₉

Tables. Length, weight, andconcUtioniiictorsK

10'

FL

for cui-ui, sexescombined,PyramidLake,Ne- vada,1976to1977 (Robertson andKoch1978).

Fork length(mm)

590

range from9 to43cm, velocities that range from 23to87cm/sec,

and

substratewithabout

60%

gravel.

Historically, cui-ui spawning runs

up

the Truckee River only occasionally reached

downtown

Reno, a distance ofover 100

km

(Snyder 1918).

Today

they generallyrun no fartherupstream than15to20

km,

although they can go further.

Koch

and Contreras (1972) report spawn-laden ^cui-ui reach ex- haustionin18, 10, 2,

and

0.5hoursatveloc- itiesof1.2, 1.8,4.6

and

5.2 m/s, respectively.

Spawning

Behavior

Spawning

cui-uioften choose the

head

of gravel bars,

where

the flowis rapidandthe substrate relatively free of silt

(McGarvey

1974). At times the dorsal fins of the cui-ui projectabovethe water,

and

inveryshallow places,

where

there is

much

crowding, the entirebacksofthefishareexposed(La Rivers 1962). Trelease (1971) notes the

numbers

of cui-ui atthe

mouth

oftheTruckee River in past years

were

so

immense

atspawning time that fishnearthe surface

were

literallyforced out of the water,

and

duringperiods ofpeak activityschools offishcovering0.4haor

more

would

form a mass ofwrithing fish on the surfaceofthe water.

Some

runs ofcui-ui

were

so extensive that, as fish

worked

their

way

upstreamindenseschools, their

numbers

ac- tuallyblockedthe flow ofwateranddivertedit

around them.

As

a result, a

new

channel was sometimescutthroughthesandydelta, leav- ing large

numbers

offishstranded.

Migratingand spawningcui-uiare

more

ac- tive atnightthanindaytime (Snyder 1918). Scoppettone et al. (1983) found that peak spawningoccurs

between

thehours2000

and

0600 overa .3-day periodandpostulate that nocturnal spawning lessens egg predation. Adhesive eggsarebroadcastovera largearea (Koch1973).

One

spawningact,lastingfrom3 to6 seconds,isparticipatedinby1, or occa- sionally 2, females and from 2 to 4 males; althoughatypicalspawningacthas 1female and2 males. Scoppettoneetal. (1983)found themostactivemale

spawned

294times, the mostactive female 114 times.

The

length of thespawning runforindividualmaleswas3to 5 days, forfemales2.5to4 days.

Just priortospawning, two malesposition themselves on either side ofa female, the

headsofthemalesjustaftofthe female's head.

With

bodiestouchingandquivering, thefe-

male deposits eggs, followed

by

the males expellingsperm.

The

cupping andvibration of the male's caudal,alongwiththe female's cau- dal,createsan

eddy

preventingtheeggsfrom drifting

away

beforetheyarefertilized(Scop- pettoneetal.1983). Althoughthecui-uidoes not builda nest,thefanningofthe caudalfins servestoclearthearea ofsilt.

Optimum

Hatching

Temperature

In an 8-day period

when

temperatures rangedfrom 13.8 to20.8 C, witha

mean

of 16.7 C,

mean

viability of the

embrvos was

47%

(Scoppettone et al. 1981).

Koch

(1981) found13.9

C optimum

forcui-uieggincuba- tion;

embryos

incubatedat17.8

C

hada

60%

survival tohatching, whereas

embryos

incu- bated at 21.7

C

had a

30%

survival.

High

temperatures cause

preemergence

oflarva,

and

alowerrateof survival(Lockheed

Ocean

Sciences Laboratories1982).

LarvalMigration

Larvalpeak

downstream

migrationis 14 or

more

daysafterhatching(Scoppettone etal. 1983). Hatchery-rearedlarval cui-ui, 15to18 days old, released in3 areas of the Truckee River,began migrating

downstream immedi-

ately.

The

peakmigrationoccurredthe night of releasefollowed

by

several days'lull. All threegroups

showed

atendencyfor

immedi-

ateoutmigration (Scoppettoneetal. 1981). It

shouldbe notedthatour embryologicalstud- ies

show

that larvae arenot developedwell

enough

tofeed or

swim

activelybefore21to 18daysat13.6C.It

may

bethatearlymigra- tions (< 28 days) greatly reduce chances of survival.

Lake

Spawning

There

are severalreports of cui-uispawning in the freshwater-lake saline interface. Snyder(1918) reports,

"On May

1, 1913large

numbers

ofcui-ui

were

founddepositingeggs along the shallowsnear

some

springsonthe southwest shore.^" Johnson (1958) observed ready-to-spawn cui-ui aroimd theperiphery of the lake.

Koch

(1973)

documented

the spawning behaviorofcui-uinearthe inflow of freshwater springs (0.014cms)in17.3

C

lake

October 1985 SiGLER ETAL.: CUI-UIIN

PYRAMID LAKE

591 Table9. Numberof cui-uieggs takenattheMarbleBluil' facility, 1978-1983(Source;Alan Rnger, Pyramid Lake Fisheries director).

Number

592

Great

BasinNaturalist Vol.45,No.4

thereis minimal; therefore, iffood supplies areadequate, thenparasites, disease,

and

se- nility are probably the most significant ad- versefactors.

Egg and

LarvaeMortality

IftheTruckee River

spawning

habitat

were

optimal,one

would

expect high hatchingsuc- cess from the river-spawning cui-ui.

How-

ever, using the fecundity of35,700 eggs per female estimated

by

Frazier

and

Ferjancic (1977), Scoppettone et al. ₍₁₉₈₁₎ projected thatif21females deposited 750,000 eggsonly 20,000larvae

would be

produced. Theiresti-

mated

survival rateto

emergence

is2.7%,this wasattributedtohigh temperatures, poor egg viability,

and

predation

by

Lahontan red- sides,Richardsoniusegregius

AdultMortality

The

highest adult mortalityprobablyoccurs duringthespawningseason,

when

cui-uiare most vulnerable to predation. Historically fishingmortality

may

or

may

not have

been

significant;itcontinuedatlowlevels, asasnag fishery ofspawnerson

and

nearthe

Truckee

RiverDelta,untilrecent years.Since1979all fishingforcui-ui,even

by

tribal

members,

is

prohibited.

Death

of adults as a result of spawning, aswellashandlingmortality dur- ing and following eggtaking at the

Marble

Bluff

and

the

PLF

facilitiesoccursat

unknown

levels. Snyder(1918) reports^afewdeadindi- viduals along the

Truckee

River after each spawningseason,

and

highmortality regularly occurredatthe

mouth

of

Winnemucca

Lake. Fish-eating birds, primarily white pelicans, Pelecanus erythrorhynchos, double-crested cormorants,Phalacrocoraxauritus,

and

Cali- forniagulls,Laruscalifornicus,can

wound

or kill adult cui-ui. Although large

numbers

of whitepelicansand cormorants

were

observed ontheTruckee River Delta duringthe 1976 and 1977 cui-ui spawning migration,

Knopf

and

Kennedy

(1980) found

no

evidencethat these birds fed on cui-ui.

Common

carp, Cyprinuscarpio,andtuichub,Gila hicolor,

composed

over

97%

of the diet of the pelican. T._J.Trelease (personal

communication

1984) states he has observed pelicans catch and swallow adultcui-ui.

The

pelicans then had greatdifficultytaking^off'withsoheavyaload.

He

also stateshehasseen several, butnot a

great

many,

cui-uiremains on

Anahoe

Island.

He

believesthemajor

damage done by

birds

ispeckingouteyesandgills. Pelicanspreyed onadult cui-uiduringthe large runof1982 (M.

LaFever

personal

communication

1983). This

phenomenon was

alsoobserved

by

D.L. Galatin recent years (personal

communica-

tion 1984).

Snyder

(1918) reports that

when

cui-uimigrateindense schoolsconsiderable

numbers

are

crowded

into shallowwater

and

even strandedout ofwater on sandbars:

Cormorants,gulls,andpelicansingreatnumbers were attackingthem,andmanystillwrigglingfisheshadlost theireyesand stripsof fleshhadbeentornfromtheir sides.

Disease

Pathological studies ofthewildcui-uipopu- lationshave not

been

conducted; therefore, theeffect of internal

and

externalparasites, fungalinfestation,

and

viral

and

bacterialdis- easeis

unknown.

Effects

ofTDS

on Eggs,Larvae,

and

Juveniles Bioassay tests conducted

by LOSE

(1982) demonstratethe intolerance offertilizedand/ orwater-hardenedcui-uieggsto

TDS

concen- trations above 525mg/1.

Embryos

placed in 525mg/1water(i.e.,

Truckee

Riverwater)for 24-96 hours survived

when

transferred to

Pyramid Lake

water (5897 mg/1), although

some

abnormalities

were

found.

Embryos

placedin5897 mg/1 water immediatelyafter fertilization in 525 mg/1water,

were

atypical within 24 hours.

An

average

90%

mortality occurredinthe5897 mg/1

TDS

concentration

by

the third day,and an averageofonly

8.3%

of the

embryos

in thisconcentration

produced

apparentlynormalfry.

One-day-oldcui-uilarvaeplacedintestcon- centrations of either 5781 or 3503 mg/1

showed

differentialmortality;

20%

and

13.3%

ofthetest fishdiedinthe respectiveconcen- trationswithin72hours.

Three

dayoldcui-ui larvaeplacedin testconcentrations of350

and

5781 mg/1had

100%

survival in thefirst 96 hours. After192hoursthere

was

nomortality inthe350mg/1level,butthe5781mg/1level had

7%

mortalityand anadditional

8%

abnor- malities.

Chronic 180-daytestsindicate thatreduced sinvival of juvenile cui-ui, across a broad rangeof

TDS

levelsextending from 3620to

October 1985 SiCLER ET^AL.:Cui-UIIN

PYRAMID LaKE

₅₉₃

5225mg/1, represents only

33%

to

48%

of the 96-hour

median

toleranceHmit(LC50).This indicates that,although

LC50

tests

may show

acutetoxicityresultingindeathonlyathigh

TDS

levels, lower

TDS

levels

may

cause death or abnormalities

when

fishareexposed forextendedperiods oftime

(LOSL

1982).

Habitat

AND Ecology

Physical

At anelevation of1154.9

_m

above

mean

sea level.

Pyramid

Lakeisapproximately40.8

km

longand from 5.8 to 17.3

km

wide, with a north-southaxis(Fig. 1). Atthis elevationit

has a surface area of437 km",a

volume

of 25.3 km^, a

mean

depthof 57.9m,anda

maximum

depthof 100.6

m

(Harris 1970).

The

onlysig- nificantinflow into the lakemostyearsisthe TruckeeRiver,

which

originates 193

km

up- streamat Lake

Tahoe

inthe Sierra Nevada. During 1976 and 1977

mean

surfacetempera- tures ranged from 6.1to 23.1 C; the lakeis

monomictic,thermallystratifying in

summer

and mixing physically during winter.

The

mostcharacteristicfeatureof

Pyramid Lake

is its high

TDS—

about 5,350'mg/1 during 1976-1977. Although

sodium

chlorideisthe dominantsaltinthe

TDS

(over70%),the lake

ishighinbicarbonatealkalinitythatisproba- bly important to the ecosystem. Since the baseload of

TDS

is relatively constant, the

TDS

ofthe lake varieswithits

volume

(Ben- son 1978b).

Temperature

The maximum

surface(0 to1

m)

watertem- peraturein

Pyramid Lake

was21.4and23.1

C

in July 1976and August 1977, respectively (Lider1978).

The

lakeisthermallystratified from June through

December;

wind-gener- ated mixing occurs from January through May.

A

metalimnion formsatdepths ranging from16to22m.

The

euphoticdepth averaged 11

m

for 1976

and

1977,

which

resultedin a trophogeniczoneofabout 4.67

km^

(Galatet al. 1981). Dissolvedoxygen

(DO)

atthesur- faceisalways near saturation, about 8 mg/1. Metalimnetic

and

hypolimnetic

_DO

deple- tionoccursbeginning_{in July,}followingstrati- fication and algal decomposition.

Maximum

DO

deficitsoccurintheprofundalzonejust priortofallmixing(Sigler etal. 1983).

Plankton

DiatomsCyclotellasp. and Stephanodiscus spp._dominatethephytoplankton

community

during winter; the most abundant chloro- phyte, Crucigenia sp., attains its

maximum

abundance

inspring.Blue-greenalgae are

by

far thedominate phytoplankton in

Pyramid

Lake (> 74%). Nodiilaria spumigena is the most abundant blue-green algae. Its

bloom

beginsasearlyasJulyandlastas late asOcto- ber. Following spring increases of algal growth, orthophosphate and nitrate are de- pleted and remain at low levels throughout the

summer.

Silica, in addition to nitrate, probablylimitsdiatom productionin

Pyramid

Lake(Galatetal. 1981). Chironomidsarethe lake'smostabundantmacroinvertebrates,fol-

lowed

by

oligochaetes, which are especially abundant in the profundal zone (Robertson 1978).

Two

euryhaline amphipods, Garn- mariislacustrisandHijallelaazteca,areasso- ciated withtufa

and

rocks.

La

Rivers (1962) reports the

Mormon

creeper,

Ambrysus

mor-

mon, common among

the rocks around the peripheryofthelake.

The

zooplankton

community

is

composed

of five cladocerans, three copepods, and four rotifers(Liderand

Langdon

1978).

The

clado- ceran,

Diaptomus

sicilis, is a perennial spe- cies

and

the most abundant zooplankton throughouttheyear.

Factors AffectingFish Activity

The

cui-uiistheleastabundantofthe four major fish species native to

Pyramid

Lake.

The

other three speciesinincreasingorderof

abundance

are Lahontan cutthroat trout,

Tahoe

sucker, andtuichub. Vigg(1981)esti- matescui-ui

compose 0.03% by numbers

and

0.47%

by weightofthefish population.

The

mean

cui-ui catch/gillnetset slightlydeclined from 1976to1977(1.29to0.95). Thisisnot a statistically significant decrease (P

=

.21).

During

1982thelargestspawning runinfive years ascended the Marble Blufffish

way

—

13,807cui-ui(Scoppettonepersonal

commu-

nication1983).Although^{it is}not

known what

proportion this spawning migration repre- sents of thetotaladult population,

now

that the fishwayisoperationalatanearconstant efficiency, themagnitudeof futurespawning